1. Field of the Invention
The present invention relates to flow through in situ reactors with suction lysimeter sampling capabilities for use in geological strata such as various subsurface soils, sediment, or other matrix, and more specifically to in situ reactors that are useful to evaluate environmental conditions required to remediate potential hazardous conditions that may occur in the soil and groundwater. The present invention is also directed to methods of using an in situ reactor with suction lysimeter sampling capabilities.
2. State of the Art
The costs associated with testing for various contaminants in soil and aquifers are well known. In situ assessment technology conventionally provides data on one treatment with respect to a contaminant. Replication of earlier testing is usually done at exorbitant monetary costs. The impact of conventional testing techniques to detect, for example, groundwater contamination has other environmental impacts on a given area and there is usually no guarantee regarding the accuracy of the resulting data. Investigators and engineers use costly laboratory tests to evaluate the efficacy of future and on-going remedial treatments.
While laboratory tests are more extensively used, these studies are also more expensive to perform and may produce ambiguous or inaccurate data because of the consequences associated with excessive soil disruption. These same laboratory tests provide no assurances that the same process will be found applicable in actual field conditions. For example, experiments that are run in a conventional manner on soil specimens or water extracted from soil specimens are not run under real time, and field conditions will not be accurately represented. Field temperatures, including temperature trends over time, will not be accurately reflected and field barometric pressures (as impacted by the in situ geology, hydrology, and stratigraphy) are not reflected. In addition, compaction and layering in the laboratory samples will impact the representiveness of the tests. Therefore, the results are questionable.
In investigating various soil contamination, it is sometimes advisable to test proposed remediation while the soil specimen remains in hydraulic contact with the underlying subsurface aquifer. Likewise, it is desirable to be able to sample the water within the pores of the soil specimen. The water in the pores is known as the soil pore water.
Conventional techniques do not allow soil specimens to maintain their biofilms and soil structures in an intact state while both the soil specimen and the soil pore water are being tested for various contamination. In this regard, traditional techniques (removing the soil for laboratory testing) have introduced reactive sites to the soil. The soil is disturbed in order to remove it for laboratory testing. Disturbing the soil may result in disturbing the various microbial communities found in the soil column. Therefore, the results of such testing are highly questionable when microbial communities are relevant to the remediation treatment being considered for a given geological strata.
One region of interest in a geological strata is a subsurface region known as the vadose zone, a region of variably saturated or unsaturated soil, sediment and rock. Water and contaminants may move through the vadose zone and eventually end up in the groundwater. Therefore, information regarding the contaminants in the vadose zone is valuable for appropriate waste treatment. A suction lysimeter is one hydrological instrument useful for sampling liquids in soil and other geological substrates, including soil in the vadose zone. There are several types of lysimeters, and the term “lysimeter” as used herein, refers to a suction lysimeter. Liquid may be drawn to the suction lysimeter using a vacuum or a pressure gradient or differential. A conventional suction lysimeter may include a filter or membrane arrangement such that undesired particulates, solids or gases are not collected with the desired sample liquid.
The sample liquid may be present in very thin layers, or the material to be sampled might be unsaturated (the pores of the material are not filled to capacity with water). If the desired liquid is not flowing freely, or held in place by capillary forces, the use of vacuum or hydraulic gradient forces may be required to overcome the capillary action and obtain the desired liquid sample. This may be required in both saturated and unsaturated sample regions.
In U.S. Pat. No. 6,681,872 to Radtke et al., an in situ reactor is described that may be placed in a borehole formed in geological strata, and receive a geological specimen derived from the geological strata. Fluids may be applied to the geological specimen to perform various experiments; however, liquid samples from the geological specimen may not be removed while the geological specimen resides in the vadose zone. In particular, liquid samples from unsaturated specimens may be desired, but may not be removed.
Therefore it would be advantageous to provide an in situ reactor with suction lysimeter sampling capabilities.